The Journal of Phytopharmacology 2023; 12(1):32-38 DOI:10.31254/phyto.2023.12105

Research Article

Evaluation of chemical compounds in Plectranthus barbatus leaves extract for application in reduction of tannery wastewater toxicity

DK Obiero¹ , JN Ombui¹ , JM Mbaria¹ , A Yenesew² , AS Onyuka³ , TN Kilee³

DK Obiero,JN Ombui,JM Mbaria,A Yenesew,AS Onyuka,TN Kilee

1. Department of Public Health Pharmacology and Toxicology, Faculty of Veterinary Medicine, University of Nairobi. P.O Box 29053- 00625, Nairobi, Kenya
2. Department of Chemistry, Faculty of Science and Technology, University of Nairobi, P.O Box 30197-00100 Nairobi, Kenya
3. Industrial Materials Research Centre, Kenya Industrial Research and Development Institute, P.O Box 30650- 00100, Nairobi, Kenya

*Author to whom correspondence should be addressed.

Received: 3rd January, 2023 / Accepted: 21st February, 2023

Abstract

Plectranthus barbatus Andr. grows in Kenya, sub-Saharan Africa, Australia, Brazil and Asia and is oneof the most important species of the Lamiaceae family. The plant is widely mentioned in traditionalmedicine in Africa and Asia. Some of the compounds previously isolated from the plant includediterpenoids, phenolic acids and essential oils. The objective of the study was to evaluate and determinethe presence of chemical compounds in Plectranthus barbatus Andr. leaves extract of tannin nature thatcan be beneficial ingredients in processing clean leather and at the same time reduce environmentalpollution. The Plant’s leaves were collected from Nyamira County then dried and ground to desiredmesh before extraction was done with water and 80 % methanol in water. The methanolic solid extractthat was recovered after freeze drying was subjected to column chromatography. The pure fractions wereanalyzed using Nuclear Magnetic Resonance spectroscopy and compared to those previously analyzedusing High Pressure Liquid Chromatography. Some of the compounds isolated include phenolics e.g.Para-Hydroxybenzoic acid and Diterpenes. Water solid extract was used in pre-tanning and re-tanningapplications followed by analysis of Biological Oxygen Demand, Chemical Oxygen Demand, pH andtotal chrome content of respective wastewaters. Tannery liquor from re-tanning and pre-tanningcombinations with Plecranthus barbatus leaves extract showed reduced toxicity to the environment withpH of 7.97 and 2.96 respectively as compared to chrome tannage liquor that recorded a relatively moreacidic pH of 2.30. Biological Oxygen Demand, Chemical Oxygen Demand and chrome content levelswere 230.00 mg/l, 4520.00 mg/l and 9.69 ppm respectively for effluent from Plectranthus barbatusretannage against 320.10 mg/l, 2331.20 and 5.03 ppm respectively from pretannage of the same extract.Permissible limits for pH, Biological Oxygen Demand, Chemical Oxygen Demand and total chrome indischarged tannery wastewater are 5.5 – 10.0, 125 mg/l – 1000 mg/l, 300 mg/l – 3000 mg/l, and 1.0 ppm– 10.0 ppm respectively. Pretanning with Plectranthus barbatus leaves extract during leather processingwas more effective is reduction of tannery wastewater toxicity although, the use of pretanning andretanning in a single tannage might yield more promising results.